JP2559267B2 - A method of simultaneously performing selective desulfurization and gasoline removal at a cryogenic temperature of a gas mixture mainly composed of methane and also including hydrocarbons of H 2 below and C 2 below. - Google Patents

Abstract

PCT No. PCT/FR88/00227 Sec. 371 Date Feb. 21, 1989 Sec. 102(e) Date Feb. 21, 1989 PCT Filed May 10, 1988 PCT Pub. No. WO88/08833 PCT Pub. Date Nov. 17, 1988.A cryogenic process of simultaneous selective desulphurization and gasoline removal of a gaseous mixture consisting mainly of methane and likewise containing H2S and hydrocarbons with C2 and more. Said gaseous mixture (1), after having eventually undergone an operation of removal of benzol (25) and then cooling (2) producing condensates (4), is washed between 0 DEG C. and -45 DEG C. by means of a solvent (5) selective of H2S to produce a current of methane (64) having a partial pressure in H2S below 65 Pa and a liquid phase (9a) rich in H2S and containing at least 80% molar of the hydrocarbons of C3 and more of the gaseous mixture (1). The liquid phase (9a) is subjected to a demethanization (29, 9) producing a demethanized rich solvent (11) and a gaseous phase rich in methane (10), the solvent (11) then is cooled between -25 DEG and -80 DEG C. sufficiently to produce its dissociation in a lower liquid fraction (38) that contains the H2S and, in methane equivalent, less than 5% molar of hydrocarbons and an upper liquid fraction (37) formed of the hydrocarbons of C3 and more. Said fractions (37, 38)are separated and the fraction (38) undergoes a regeneration (46, 16, 20) to produce a current (24) of acid gas rich in H2S and containing the small amount cited above of hydrocarbons and a regenerated solvent (21).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is comprised primarily of methane, also includes H ₂ S and C _{2 and} higher hydrocarbons, optionally with an inert gas, H ₂ O, C.
The present invention relates to a method for simultaneously carrying out selective desulfurization and gasoline removal of a gas mixture containing one or more compounds of O ₂ , COS and mercaptan under an absolute pressure of more than 0.5 MPa at a cryogenic temperature. The method of the present invention, allowed to separate direct the type of gas mixture into three components of the following: - mainly consists of methane, H ₂ S partial pressure less than 65 Pa, the gas mixture to be treated is other than H ₂ S Treated gas having a total partial pressure of sulfur-containing compounds of less than 260 Pa when containing COS and / or methane.

Heavy hydrocarbon fraction containing at least 80 mol% of C _{3 and} above hydrocarbons present in the gas mixture to be treated.

An acidic gas stream consisting of H ₂ S, which may be mixed with more or less large amounts of the acidic compounds CO ₂ , COS and mercaptans. This acid gas stream should be treated with less than 5 mol% of hydrocarbons, expressed as methane equivalents, of H ₂ S and other acid compounds, if the compounds are present in the gas mixture to be treated. 80% of H ₂ S contained in the gas mixture
H ₂ including the above and greater than the gas mixture to be treated
It has an S: CO ₂ molar ratio.

Numerous industrial processes are known for the treatment of gas mixtures such as those mentioned above, represented by various natural gases. These methods include deacidification (dsacidifica
operation), that is, the operation of removing H ₂ S and other acid gases,
Gasoline removal Dgazolinage), i.e. the includes a gas mixture for example an operation and to separate the C ₃ and heavier hydrocarbons, allowed to fractionate the gas mixture into three components such as described above. The deacidification and gasoline removal operations are usually performed separately and form part of a series of operations performed on the gas mixture to be treated. These series of operations are mainly
Cryogenic distillation at -30 ° C to -90 ° C optionally combined with acid gas removal, drying, water adsorption on suitable solids such as molecular sieves, extraction with solvent to obtain natural gas liquid fractions And the reheating of the treated gas to room temperature in order to supply it to the gas distribution network. In the above-mentioned treatment methods of natural gas type gas mixtures containing the above constituents, it is necessary to lower the temperature of the gas mixture only during the production of the natural gas liquid fraction, and other operations are not carried out at such low temperatures. Absent.

This type of processing method has major problems in performing multiple operations sequentially on the basis of very different principles and at various temperatures. Since there is almost no possibility of unifying temperatures, the processing cost is extremely high in terms of energy and investment. It also generally corresponds to the first step of the process and is usually a solvent of acidic gas compounds which is selective or non-selective with respect to H ₂ S and which is reproducible, for example aqueous solutions of alkanolamines or potassium carbonate or Even in the acidic gas compound removal step consisting of washing the gas mixture to be treated (to be treated) in countercurrent with an organic solvent, if the gas mixture to be treated contains C ₃ or more hydrocarbons, The selection range of the solvent is also limited when the amount is sufficiently small.

In fact, industrially available can and effectively dissolve it organic solvent with acid compounds and mercaptans such as in addition to CO _2, COS of H ₂ S, for example propylene carbonate, methanol, N- methylpyrrolidone, ethylene glycol or C ₄ ~ C ₁₂
Organic solvents such as dimethyl ether of polyethylene glycol can be used only when the hydrocarbon content of the gas mixture to be treated is very low. If not used, most of the hydrocarbons above C ₃ will be absorbed by the organic solvent and included in the H ₂ S-containing acidic gas stream generated during solvent regeneration, and as a result, generally As mentioned above, when using the acidic gas in a sulfur factory,
The function of the factory is hindered. Therefore, it is preferable to use a solvent consisting of an aqueous solution of an amine, especially an alkanolamine or potassium carbonate, and avoid using an organic solvent.

As a method of treating a natural gas type gas mixture, there is also known a method of simultaneously removing an acidic gas contained in the gas mixture and producing a gaseous hydrocarbon and a liquid hydrocarbon. This type of treatment is called the RYAN-HOLMES method,
CHEMICAL ENGINEEFRNG by J.RYAN and F.SCHAFFERT
PROGRESS, October 1984, pages 53-56. In this type of process, the natural gas to be treated is conventionally dehydrated and frozen and then subjected to cryogenic distillation, which is carried out in three or four consecutive operating steps. When this distillation operation is performed in three steps, the first column (methane removal column (dmthaniseur)) is injected with an additive consisting of a liquid fraction of C ₄ or more hydrocarbons at the head, and the dehydration-freezing is performed. Natural gas is separated into a gas phase containing methane and lighter compounds and a liquid fraction containing C _{2 and} higher hydrocarbons and acid gases. Then the second
Column (ethane removal column (d-thaniseur))
At the same time, the liquid fraction is separated into an upper fraction containing CO ₂ and a lower fraction containing C ₂ or more hydrocarbons and H ₂ S while introducing an appropriate amount of the additive. The lower fraction is further in the third column, H ₂ S
Separation into an upper fraction consisting of a C ₂ -C ₄ hydrocarbon liquid fraction contained and a lower fraction consisting of a C ₄ or higher hydrocarbon liquid fraction. This lower fraction contains most of the butane and higher hydrocarbons present in the hot gas for treatment, a suitable amount of which is taken from the lower fraction
And as an additive to be injected into the second column. The use of such an additive avoids CO ₂ crystallization at the head of the methane removal column and ensures that the azeotropic state formed between ethane and CO ₂ is destroyed and these compounds are removed from the ethane removal column. It will be easily separated within. Then
If washing the H ₂ S-containing C ₂ -C ₄ fractions hydrocarbon liquids in aqueous amine solution comprises CO ₂ is a C ₂ -C ₄ hydrocarbons purified liquid fraction, optionally in addition to H ₂ S, CLAUS An acid gas stream is obtained which can be used for sulfur production in the unit.

This type of method uses CO ₂ at the head of the methane removal column.
Avoiding crystallization of ethane and CO in ethane removal column
_The operation is more complicated to carry out and therefore also more expensive to carry, since additives have to be used to destroy the azeotropic state between the _two .

Acid gas contained in natural gas, especially H ₂ S, is generally −1.
It is also known to be removable by washing with a solvent such as methanol at operating temperatures below 0 ° C. In particular, the literature
FR-A-255956 discloses a method of this type, in which natural gas scrubbing with cold methanol is carried out in a plurality of scrubbing zones. These cleaning zones are arranged in series, and the operating temperature therein is preferentially reduced from upstream to downstream in each zone. The natural gas to be treated is introduced at the entrance of the first zone and passes through each zone in sequence,
It is discharged from the final zone with the acid gas concentration greatly reduced. On the other hand, low temperature methanol is injected into each zone and separated from natural gas at the outlet of the corresponding zone. The methanol injected into each zone other than the final zone is used methanol separated at the outlet of the zone immediately downstream of the corresponding zone, and the methanol separated from the first zone is supplied to the final zone after regeneration. The natural gas can be subjected to a purification treatment by permeation before the washing treatment of methanol, in particular for the purpose of removing a certain amount of acid gas, and the natural gas after washing with methanol, namely H ₂ S.
Natural gas containing almost no hydrogen can be subjected to a liquefaction process. Refined natural gas can also be subjected to conventional gasoline removal treatments, but there is no mention of this treatment in the literature.
The document also does not specify the hydrocarbon content of the acid gas produced by the regeneration of the solvent. As is well known, the concentration is one of the important factors involved in the successful functioning of a sulfur plant that treats the acid gas.

The present invention is a gas mixture of natural gas type, i.e. mainly consists of methane, also contain H ₂ S and C ₂ or more hydrocarbons,
Optionally containing one or more gaseous compounds of inert gas, H ₂ O, CO ₂ , COS and mercaptan, and 0.5M
We propose a method to perform selective desulfurization and gasoline removal treatment of gas mixture under absolute pressure higher than Pa simultaneously at cryogenic temperature. This method involves adding a gas mixture to a treated gas consisting of three components as described above, namely mainly methane,
The purpose of separating the heavy hydrocarbon liquid fraction and the H ₂ S-containing acid gas stream can be achieved more easily and at lower cost than known methods.

The method of the present invention, solvents such as following in the cleaning zone such gaseous mixtures of the foregoing, namely H ₂ S, the COS and mercaptans dissolved preferentially, CO ₂ dissolves only partially, the boiling point at atmospheric pressure is 40 It is a method of a type of contacting a solvent having a viscosity higher than 0.1 ° C and a viscosity at -40 ° C of less than 0.1 Pa.s, and regenerating the solvent having absorbed H ₂ S and other compounds, wherein the gas mixture and the solvent are mixed. Touch operation at a sufficiently low temperature,
In addition, the mass flow rate ratio of the gas mixture and solvent to be used and the theoretical plate number for cleaning are mainly composed of methane and the H ₂ S partial pressure is 65 Pa.
A smaller, treated gas with a total partial pressure of sulfur-containing compounds of less than 260 Pa if the gas mixture to be treated also contains COS and / or mercaptans, and high concentrations of H ₂ S and other absorbing compounds The solvent and the liquid phase referred to as the solvent riche consisting of a condensed hydrocarbon fraction corresponding to 80 mol% or more of the C ₃ or more hydrocarbons present in the process gas mixture are selected to form a liquid phase called a solvent riche. The rich solvent is subjected to at least partial methane removal treatment to form a liquid phase called a methane removal rich solvent having a reduced methane concentration and a gas phase having a high methane concentration, and the gas phase before contacting with the solvent It is optionally combined with the treatment mixture and the methane removal rich solvent is cooled to a temperature well below the temperature in the wash zone to produce its component dmixtion. By, in addition to COS dissolved in the solvent, CO ₂ and mercaptans also optionally comprise and lower purified rich solvent than 5 mole% of dissolved acidic compound amount represents a hydrocarbon content of methane equivalents of the acidic compound H ₂ S Forming a lower liquid fraction referred to as the upper liquid fraction referred to as a heavy hydrocarbon first fraction consisting of the remainder of the hydrocarbons present in the methane removal rich solvent, said heavy hydrocarbon first fraction Is separated from the purified rich solvent, the purified rich solvent is subjected to a regeneration treatment, containing almost all of H ₂ S and other acidic compounds optionally present in the purified rich solvent, and represented by methane equivalents. It is characterized in that an acidic gas stream containing less than 5 mol% of hydrocarbons of the acidic compound and a regenerating solvent are formed and the regenerating solvent is recycled in the direction of the washing zone.

In the present invention, the "quivalent mthan equivalent (quivalent mthan
e) "means a pseudo-molc molecule containing only one carbon atom, which is the same as the number of carbon atoms in the hydrocarbon molecule.
ules).

The solvent as mentioned above, which is brought into contact with the processing gas mixture for absorbing H ₂ S and other compounds COS and mercaptans, preferably has a viscosity of less than 0.05 Pa.s.

The solvent used in the present invention is substantially greater than the capability selective solvents regard H ₂ S, i.e. the ability to absorb the H ₂ S and other sulfur-containing compounds, such as described above absorbs CO _2,
Thus, the solvent is such that the molar ratio of H ₂ S and other sulfur-containing compounds to CO _{2 in} the acid gas stream generated during solvent regeneration is greater than the molar ratio in the gas mixture to be treated.

The solvent used in the present invention may in particular consist of one or more liquid absorbents used in anhydrous form or in the form of a mixture with water. One or more of these solvents, the following formula An amine represented by the following formula An aldehyde represented by the formula below Acetal represented by the formula below In ester represented, C1 -C4 alkanols, diethers of formula _{CH 3 OC 2 H 4 O n} CH 3, diether alcohols of the formula _{R 9 OC 2 H 4 -O-} C 2 H 4 -OH, wherein Selected from lactones and propylene carbonate. However, in the above formula, R ₁ and R ₂ are the same or different from each other, and are a hydrogen atom or C ₁
Or an alkyl group of C _2, R ₃ is alkyl of C ₃ or C _4, R ₄ and R ₅ are the same or different from one another, C ₁
Represents an alkyl group of -C _3, R ₆ is C alkyl group or a group C ₂ of _{2 ~C 4 H 4 O n R} 8 [ wherein R ₈ represents an alkyl group of C ₁ or C _2, n is 1 Or equal to 2], R ₇ is C ₁ or C ₂
An alkyl group or a group _{C 2 H 4 O n R 8} , R 9 is an alkyl group of C ₁ ~C _4, p is an integer of 2 to 4.

Non-limiting specific examples of the liquid organic absorbent corresponding to the above formulas, N, N-dimethylformamide, N, N-dimethylacetamide, dimethoxymethane, diethoxymethane, 1,1-dimethoxyethane, methanol, Mention may be made of ethanol, dimethyl ether of ethylene glycol, dimethyl ether of diethylene glycol, monomethyl ether of ethylene glycol, butyrolactone, propiolactone and propylene carbonate.

The temperature at which the processing gas mixture is brought into contact with the solvent in the cleaning zone is preferably 0 ° C to -45 ° C.

The wash zone consists of one or more wash columns, each column advantageously containing about 10 or more, preferably 20 or more, stage tage thoriques. These columns are, for example, plate column type or packed column type. Advantageously, the temperature in each wash column is preferably maintained within ± 5 ° C. error by indirect heat exchange occurring at one or more points in the column between the fluid medium and the cooling fluid in that column. Is.

In one particular embodiment of the process according to the invention, the gas mixture to be treated is cooled to a temperature of 0 ° C. to −30 ° C. before it is brought into contact with the solvent, predominantly C _{3 and} above hydrocarbons and H ₂ S. Forming a liquid phase referred to as condensats and a gas phase referred to as a pretreatment gas mixture, and then contacting the pretreatment gas mixture with a solvent in a scrub zone and removing the solvent exiting the scrub zone. A rich solvent is formed with the condensate resulting from the cooling step and the rich solvent is subjected to a methane removal treatment.

In another particular embodiment of the process of the present invention, the gas mixture to be treated is cooled to a temperature of 0 ° C. to −30 ° C. before it is contacted with a solvent, mainly to remove hydrocarbons above C ₃ and H ₂ S. Forming a liquid phase called a condensate containing and a gas phase called a pre-treatment gas mixture, then contacting the pre-treatment gas mixture with a solvent in a washing zone, a liquid phase consisting of the solvent leaving the washing zone, The liquid phase consisting of the condensate resulting from the cooling step is treated separately for methane removal, and the solvent and condensate after these separate methane treatments are combined to form a methane removal rich solvent. The gas phases produced during the methane removal process are preferably separately or mixed and recycled to the process gas mixture upstream of the cooling stage.

The methane removal process applied to rich solvents and condensates is 2
It is advantageous to carry out in one step. That is, in the first step, a fluid to be demethane removed, that is, a rich solvent or a condensate, is subjected to a first dtente treatment in which it is expanded to an intermediate pressure suitable for releasing most of methane dissolved in the fluid. A first high methane concentration gas and a methane pre-removal fluid are formed, and in a second step, the methane pre-removal fluid is subjected to a second expansion treatment and then a distillation treatment to obtain a second high methane concentration gas and a methane removal fluid. And form. The second methane-rich gas is compressed to the pressure of the first methane-rich gas and then mixed with the first methane-rich gas to form a methane-rich gas phase. This gas phase is optionally recycled to the process gas mixture.
In the second step of the methane removal process, the second expansion process is followed by a distillation process in which a fluid consisting of at least a portion of the gas mixture taken from the process gas mixture prior to contact with the solvent or prior to cooling, or regenerated solvent Preference is given to carrying out a reboil with at least two reboil zones arranged in series with a one-part fluid.

The temperature for cooling the solvent to a temperature lower than the temperature of the methane removal rich solvent in order to cause mutual separation of the constituent parts of the solvent is advantageously −25 ° C. to −80 ° C.

Regeneration of the purified rich solvent can release the gaseous compounds dissolved in the liquid and can be carried out by any process such as expansion and / or distillation. The regeneration treatment of the purified rich solvent especially comprises expanding the purified rich solvent to a pressure higher than 100 KPa, preferably a pressure of 150 KPa to 300 KPa, and then subjecting said expanded solvent to at least one partial evaporation treatment to obtain at least one acidic gas fraction. A partial regeneration step to form a semi-regenerated solvent whose temperature is at least 0 ° C. and whose pressure is less than that of the expanded solvent and which is equal to at least 100 KPa, and the semi-regenerated solvent is completely removed by distillation mainly using reboiling. It may include a complete regeneration step of regeneration to form the acid gas fraction and the regeneration solvent. The regenerated solvent, after proper cooling, is recycled to the wash zone and the various acid gas fractions are combined into an acid gas stream. The hydrocarbon concentration of this acid gas stream, expressed in methane equivalents, is lower than 5 mol% of the acid compounds.

In the partial regeneration step of the purified rich solvent, it is advantageous to carry out the partial evaporation treatment of the expanded solvent as follows.
That is, first, the solvent is subjected to a first partial evaporation treatment,
Forming a first acid gas fraction and a first liquid phase having a temperature below 0 ° C., and then subjecting said first liquid phase to a second partial evaporation process to obtain a second acid gas fraction and a temperature Form a second liquid phase having a temperature of 0 ° C. or higher and a pressure lower than that of the expanding solvent and being equal to at least 100 KPa. The second liquid phase is treated as a semi-regenerated solvent in a complete regeneration step, and the first acid gas fraction is heated to a temperature of 0 ° C. or higher, and then the second acid gas fraction and the semi-regenerated solvent are completely regenerated. Combined with the resulting acid gas fraction to form an acid gas stream having a hydrocarbon content, expressed in methane equivalents, of less than 5 mol% of the acid compound.

The complete regeneration treatment of the semi-regenerated solvent by distillation is carried out using a column which comprises a plurality of theoretical stages, so that the regenerated solvent is discharged from the bottom.

In this case, the semi-regenerated solvent may separate into two streams. One stream is sent to the head plate of the distillation column, the other stream is reheated countercurrently with the regenerated solvent discharged from the column before it is introduced to the intermediate theoretical plate level of the column.

Prior to regeneration of the purified rich solvent, a supplemental treatment to remove hydrocarbons may be applied. This process is preferably 4
A first liquid-liquid extraction zone comprising one or more theoretical stages for extraction, in which the solvent is contacted with an extractant consisting mainly of a hydrocarbon having a molecular mass greater than n-pentane, and the solvent is extracted from the purified rich solvent to a second one. The hydrocarbon liquid fraction is separated and this second
The fractions were combined with the first heavy hydrocarbon fraction, The mixture thus formed by and distillation was heated, 80 moles of C ₃ and higher hydrocarbons present in the process gas mixture %
A heavy hydrocarbon fraction containing the above is formed, the extractant is recovered, and most of the extractant is cooled to a temperature substantially the same as the temperature at which mutual separation of constituent components of the methane removal rich solvent occurs, and then the first Recirculating in the direction of the liquid-liquid extraction zone.

Advantageously, the treated gas exiting the wash zone is cooled by at least 15 ° C. to form a cooled treated gas and a liquid fraction, which liquid fraction is mixed with a rich solvent and subjected to a methane removal treatment. The cooled processed gas is subjected to a complementary extraction process in a complementary extraction zone with an amount of extractant not used in the first extraction zone to form a more pure processed gas and liquid fraction. May be. The liquid fraction is recycled for use in distilling a mixture of first and second hydrocarbon cuts.

Prior to all treatments, the treatment gas mixture was subjected to a drying and dibenzolage operation by distillation and contact with an anhydrous solvent to give a dry gas mixture having an aromatic hydrocarbon content, in particular benzene, of less than 0.1% by weight. It is also possible to form a hydrocarbon fraction containing a liquid consisting of a majority of the aromatic hydrocarbons and water-containing solvent present in the treatment gas mixture.

In order to make the present invention more apparent, three embodiments of the present invention using the apparatus briefly shown in FIGS. 1 to 4 of the accompanying drawings will be described below.

FIG. 1 shows that the processing gas mixture supplied through the conduit 1 is cooled in the cooling zone 2 to a temperature of, for example, 0 ° C. to −30 ° C., and mainly in the separator 2a, hydrocarbons having C ₃ or higher and The liquid phase, which is called the condensate, which contains H ₂ S and is to be discharged from the bottom of the separator via the conduit 4, and the pretreatment gas mixture which is discharged from the head of the separator via the conduit 3 Separated into gas phase. The pretreatment gas mixture is introduced into the lower part of the washing column 5, which preferably comprises at least 20 theoretical stages for washing, in which the solvent injected via the conduit 6 into the upper part of the column 5 is introduced. And in countercurrent contact with.
This contact is carried out, for example, at a temperature of 0 ° C to -45 ° C. At the top of the column 5, the treated gas, which consists mainly of methane and has a reduced H ₂ S concentration, is recovered via the conduit 7, and at the bottom of the column a solvent containing high concentrations of H ₂ S and other absorption compounds. The liquid phase consisting of is discharged via conduit 8. In the conduit 9a, the liquid phase combines with the condensate discharged from the separator 2a via the conduit 4 to form a liquid phase called a rich solvent. The final temperature of the cooling treatment in zone 2 is selected in the range of 0 ° C to -30 ° C, and the contact between the pretreatment gas mixture and the solvent in the column 5 is performed at a sufficiently low temperature in the range of 0 ° C to -45 ° C. To implement.
Also, the mass flow ratio of the processing gas mixture and the solvent (rappor
t des dbits massiques) is a H ₂ S gas whose treated gas recovered at the head of column 5 via conduit 7 is less than 65 Pa.
To have a partial pressure of less than 260 Pa if the gas mixture to be treated contains COS and / or mercaptans in addition to H ₂ S, and conduit 9a
Rich solvent passing through is present in the gas mixture to be treated
It is selected to contain at least 80 mol% of C _{3 and} above hydrocarbons.

The rich solvent flowing through the conduit 9a is introduced into the upper part of the methane removal column 9 consisting of a reboil distillation column, and in this column, a gas phase having a high methane concentration and a liquid phase called a methane removal rich solvent having a low methane concentration are formed. The gas phase is discharged from the top of the column 9 via conduit 10 and the liquid phase is discharged from the bottom of the column via conduit 11. The methane removal rich solvent is sent to the cooling zone 12 where it is cooled to a temperature, for example in the range of -25 ° C to -80 ° C and well below the temperature in the wash zone 5. As a result, mutual separation of constituent parts of the methane removal rich solvent occurs, so that the solvent is separated in the separator 12a, the lower liquid fraction is discharged from the separator via the conduit 14, and the upper liquid fraction is discharged. It is discharged from the separator 12a via the conduit 13. The lower liquid fraction is referred to as a refined rich solvent and optionally contains CO ₂ , COS and mercaptan dissolved in a solvent in addition to the acidic compound H ₂ S, and represents 5 mol% of the acidic compound in terms of methane equivalent of hydrocarbons. Including less than. Further, the upper liquid fraction is referred to as a heavy first hydrocarbon fraction, and is composed of the remaining hydrocarbons existing in the methane removal rich solvent, and carbonization of C ₃ or more contained in the processing gas mixture. Contains 80 mol% or more of hydrogen.

The purified rich solvent is then expanded by passing through expansion valve 15 to a pressure above 100 KPa, preferably between 150 KPa and 300 KPa, where the expanded solvent passes through reheater 16 where it is subjected to partial evaporation. The fluid resulting from this evaporation process is sent to the separator 16a, as a result of which the acidic gas fraction is discharged from the head of said separator via conduit 17 and from the bottom is called semi-regenerated solvent via conduit 18. The liquid is drained. The expansion treatment of the purified rich solvent for partially regenerating the purified rich solvent and the partial evaporation treatment of the expanded solvent are such that the temperature is 0 ° C. or higher and the pressure is 100 KPa or higher, which is smaller than the pressure of the expanded solvent. Carry out so that a semi-regenerated solvent is obtained. It is introduced into the upper part of the semi-regenerated solvent reboiler distillation column through line 18 and is completely regenerated in this column. The semi-regenerated solvent is separated by distillation in the column 20 into an acidic gas fraction and a regenerated solvent, the acidic gas fraction is discharged from the head of the column via a conduit 19, and the regenerated solvent via a conduit 21. Drains from the bottom of the column. This regenerated solvent is in the cooling zone
After cooling to a suitable temperature at 22, it is reintroduced into the image column 5 via conduit 6.

The acidic gas fraction discharged from the head of the separator 16a via the conduit 17 and the acidic gas fraction discharged from the column 20 via the conduit 19 join together to form an acidic gas stream. The hydrocarbon content of this gas stream is less than 5 mol% of acidic compounds, expressed in methane equivalents.

The treated gas recovered at the temperature in the cleaning zone 5 via the conduit 7 is, after reheating, or if necessary, one or more additional treatments, for example CO ₂ which may still be present in the gas. washing with a suitable solvent for recovering or C ₂ -C ₃
It may be sent to a feed network after being subjected to treatment with a turbo expander to recover hydrocarbons. The hydrocarbon separated and recovered from the treated gas joins the heavy hydrocarbon fraction discharged from the separator 12a via the conduit 13.

In FIG. 2, the gas mixture to be treated is introduced via the conduit 1 and cooled in the cooling zone 2 to a temperature of, for example, 0 ° C. to −30 ° C., in the separator 2a mainly hydrocarbons of C _{3 and} above. And H ₂
A liquid phase, called the condensate, which will be discharged from the bottom of the separator via a conduit 4 containing S, and a gas phase, called the pre-treated gas mixture, flowing out of the head of the separator via conduit 3. Is separated into The pretreatment gas mixture is at least
Introduced into the lower part of the washing column 5, which preferably comprises 20 theoretical wash stages, in which the solvent is countercurrently contacted with the solvent injected via conduit 6 into the lower part of the column 5. This contact is carried out, for example, at a temperature of 0 ° C to -45 ° C. At the top of the column 5, the treated gas, which consists mainly of methane and has a reduced H ₂ S concentration, is recovered via the conduit 64, and at the bottom of the column a solvent containing high concentrations of H ₂ S and other absorption compounds. The liquid phase consisting of is discharged via conduit 8. conduit
Processed gas flowing through 64 is at least 15 in cooling zone 55
It is cooled by ° C and then flows into separator 56 where it is separated into a gas phase and a liquid phase due to the supplemental cooling in zone 55. The vapor phase is recovered from the head of the separator 56 via conduit 7 and the liquid phase is discharged from the bottom of the separator via conduit 57. H ₂ S discharged from column 5 via conduit 8
The solvent having a high concentration of other acidic compounds and the condensate discharged from the separator 2a via the conduit 4 join together to form a liquid phase called a rich solvent, and the separator 56 is added to this liquid phase.
The liquid fraction discharged from is added via conduit 57 and the mixture thus formed flows through conduit 9a. The final temperature of the cooling treatment in zone 2 is selected in the range of 0 ° C to -30 ° C, and the contact between the pretreatment gas mixture and the solvent in the column 5 is performed at a sufficiently low temperature in the range of 0 ° C to -45 ° C. To implement. Further, the mass flow ratio of the processing gas mixture and the solvent is determined by the conduit 64.
The treated gas collected at the head of the column 5 via the
H ₂ S partial pressure less than Pa, the gas mixture to be treated is H 2
_{In the} case of containing COS and / or mercaptan other than ₂ S, it has a total partial pressure of sulfur-containing compound of less than 260 Pa, and the rich solvent passing through the conduit 9a has a C ₃ or more amount of C ₃ or more present in the processing gas mixture. It is selected to contain at least 80 mol% of hydrocarbons. The column 5 comprises two coolers 61 through which the fluid medium, ie the mixture of solvent and gas to be treated, passes, through which said medium indirectly exchanges heat with the cooling fluid. The temperature rise of the medium due to absorption is limited and the temperature profile in the column becomes uniform within an error of ± 5 ° C.

The rich solvent flowing through conduit 9a is introduced into the upper portion of expansion flask 29 where it expands to an intermediate pressure which releases much of the methane dissolved in the rich solvent, resulting in the first high methane concentration gas and methane pre-removal. A rich solvent is formed. The first enriched methane gas exits the top of flask 29 via conduit 34 and the methane pre-removal rich solvent exits the bottom of flask 29 via conduit 35.

The methane pre-removal rich solvent is subjected to a second expansion treatment and further subjected to a distillation treatment in the distillation column 9. This distillation process involves reboiling 30 in two reboilers 30a and 30b arranged in series with a reboiling fluid 31 consisting of at least a portion of the gas mixture to be treated or at least a portion of the regenerating solvent, As a result, a second high methane concentration gas discharged from the head of the column 9 via the conduit 32 and a methane-removed rich solvent with a reduced methane concentration discharged from the bottom of the column 9 via the conduit 11 are referred to. And forming a liquid phase. The second methane-rich gas flowing in conduit 32 is sent to compressor 33, resulting in conduit 36 at about the same pressure as the first methane-rich gas flowing in conduit 34.
Is discharged from the compressor via. The two methane-enriched gases are mixed in the conduit 10 and the gas phase consisting of this mixture is passed through the compressor 23 to the processing gas mixture introduced via the conduit 1 for reuse.

The methane removal rich solvent is sent to the cooling zone 12,
Then, for example, it is cooled to a temperature in the range of -25 ° C to -80 ° C and sufficiently lower than the temperature in the cleaning zone 5. As a result, component separation of the methane removal rich solvent occurs, so that the solvent is separated into a lower liquid fraction and an upper liquid fraction in the separator 12a. Said lower liquid fraction is referred to as the pre-purified solvent and in addition to the oxidizing compound H ₂ S optionally also CO ₂ , COS and mercaptan,
It also consists of a solution containing a small amount of hydrocarbons and is discharged from the separator via conduit 38. The upper liquid fraction, also referred to as the heavy first hydrocarbon fraction, is discharged from the separator 12a via conduit 37. The pre-purified solvent is introduced into the upper part of the first liquid-liquid extraction zone 39 containing four or more theoretical plates for extraction, where it flows countercurrently with the extractant introduced into the lower part of zone 39 via conduit 40. Touch the formula.

The extractant consists primarily of hydrocarbons with a molecular mass greater than n-pentane. By this extraction process,
A second liquid fraction of hydrocarbons and a refined rich solvent are formed, said second liquid fraction is discharged from extraction zone 39 via conduit 62 and said purified rich solvent is discharged from zone 39 via conduit 14. To be done. This refined rich solvent is an acidic compound
In addition to H ₂ S, CO ₂ , COS, and mercaptan are optionally contained in a dissolved state, and hydrocarbon is also represented by methane equivalent and is included in an amount of less than 5 mol% of the acidic compound. The second hydrocarbon fraction flowing in conduit 62 joins the first hydrocarbon fraction flowing in conduit 37,
The mixture thus formed is passed through a reheater 41 to a distillation column 42 where it is fractionated. As a result, from the head of column 42, the C ₃ present in the process gas mixture is
The heavy hydrocarbon fraction containing 80 mol% or more of the above hydrocarbons is discharged via the conduit 13, and the extractant is recovered from the bottom of the column via the conduit 43. Most of the extractant is cooled in cooling zone 44 to about the same temperature as in intermixing zone 12 and then sent via conduit 40 toward extraction zone 39 for reuse. The rest of the extractant is extracted via conduit 45.

The purified rich solvent flowing through the conduit 14 is passed through the expansion valve 15 to a pressure greater than 100 KPa, preferably 150 KPa.
It is expanded to a pressure of ~ 300 KPa and the expanded solvent is subjected to a first partial evaporation process in a first reheater 46. The fluid produced by this first partial evaporation process is sent to the separator 48a, so that the head of the separator discharges the first acid gas fraction via conduit 47 and the bottom from conduit 50. The first liquid phase with a temperature below 0 ° C. is discharged. The first
The liquid phase is then sent to the second reheater 16 where it undergoes a second partial evaporation process. The fluid produced by this second partial evaporation process is sent to the separator 16a, so that the second acid gas fraction is discharged from the head of the separator via conduit 17 and from the bottom via conduit 18. A second liquid phase, called the semi-regenerated solvent, is discharged. The semi-regenerated solvent has a temperature above 0 ° C. and a pressure less than that of the expanded solvent and at least equal to 100 KPa. This series of operations constitutes a partial regeneration step of the purified rich solvent. The semi-regenerated solvent is then subjected to a complete regeneration treatment. To do so, the semi-regenerated solvent flowing out of the separator 16a via conduit 18 is split into two streams, one of which is fitted with conduit 51 in the head plate of a reboiler distillation column 20 containing a plurality of theoretical stages. And the other stream is reheated in the indirect heat exchanger 52a and then injected via conduit 52 to the midpoint of the column. In the column 20, the semi-regenerated solvent is separated by distillation into an acidic gas fraction and a regenerated solvent, and the acidic gas fraction is introduced into the conduit 19
Is discharged from the head of the column via the column, and the regenerated solvent is discharged from the bottom of the column via the conduit 21. This regenerated solvent passes through the cooling zone 22 and via the conduit 6 into the washing column 5
Used in heat exchanger 52a to reheat the stream of semi-regenerated solvent injected into column 20 via conduit 52 before being reintroduced therein, so that the temperature of the regenerated solvent injects into column 5. To a temperature suitable for.

The first acid gas fraction discharged from separator 46a via conduit 47 was heated to a temperature above 0 ° C. in reheater 49 and then in conduit 48 discharged from separator 16a via conduit 17 It joins the second acid gas fraction and the acid gas fraction discharged from the complete regeneration column 20 via conduit 19. The mixture of these three acidic gas fractions constitutes the acidic gas stream produced by the process as described above, ie the acidic gas stream having a hydrocarbon content, expressed in methane equivalents, of less than 5 mol% of the acidic compounds.

The treated gas recovered at the temperature in separator 56 via conduit 7 may be reheated or, if desired, one or more additional treatments as described in the embodiment according to FIG. It can be sent to a supply network after it has been subjected to steaming.

The embodiment of the method according to the invention shown in FIG. 3 comprises, in addition to all the operating steps of the embodiment described on the basis of FIG. 2, the treatment gas mixture is dried and benzol prior to all operations. It includes a step of removing the gas and a step of subjecting the cooled gas recovered from the head of the separator 56 to an extraction process for further purification.

The process gas mixture introduced via conduit 1 is sent to the lower part of the reboil column 25 where it comes into countercurrent contact with the solvent injected via conduit 54 which communicates with the upper part of the column 25. The solvent is cooled in the cooling zone 2 downstream of the heat exchanger 52a.
It was collected from the regenerated solvent before passing through 2. As a result of this contact, the content of aromatic hydrocarbons, especially benzene, is 0.
Less than 1% by weight of dry gas mixture in column 2 via conduit 26
The aromatic hydrocarbon-containing fraction, which contains the majority of the aromatic hydrocarbons present in the process gas mixture, discharged from 5, is piped.
The liquid, which is discharged from the column 25 via 27 and is composed of the solvent that has absorbed water, is discharged from the column 25 via the conduit 28.

The dry gas mixture flowing in conduit 26 is then
It undergoes the same treatment as the gas mixture introduced via conduit 1 in the embodiment shown. However, in this case, the washing column 5
The three chillers 61 in the column are used to control the temperature in the column, and the high methane concentration gas phase flowing in the conduit 10 resulting from the methane removal process is dried and removed in the benzene removal column 25.
It is sent in the direction of the processing gas mixture before it is introduced into the reactor and reused.

Chilled gas exiting separator 56 is introduced via conduit 58 into the lower portion of supplemental extraction zone 60 where it comes into countercurrent contact with the extractant injected into the upper portion of the column. As a result, the treated gas of higher purity is discharged from the head of zone 60 via conduit 7 and the liquid fraction is discharged from the bottom of zone 60 via conduit 61,
This liquid fraction joins the mixture of the first and second hydrocarbon cuts sent to the reheater 41. As the extractant to be injected into the extraction zone 60, a part of the extractant extracted from the distillation column 42, which is not supplied to the first extraction zone 39, is used after being cooled in the cooling zone 59.

The treated gas recovered at the temperature in the extraction zone 60 via the conduit 7 is reheated, or if desired, a first gas.
It may be sent to the supply network after being subjected to one or more supplemental treatments as described in the embodiments of FIGS.

In Figure 4, the process gas mixture supplied through conduit 1 is introduced into the lower portion of the tower 70, where for example for example is cooled to a temperature of 0 ℃ ~-30 ℃, mainly C ₃ or more carbon It is separated into a liquid phase called condensate containing hydrogen and H ₂ S and a gas phase called a pretreatment gas mixture, said liquid phase being discharged from the bottom of column 70 via conduit 71, said gas phase being Exits from the head of tower 70 via 3. The pretreatment gas mixture is introduced into the lower part of the scrubbing column 5, which preferably comprises more than 20 scrubbing logic stages, where it countercurrently flows with the cryogenic solvent injected into the upper part of the column 5 via conduit 6. Contact. This contact is carried out, for example, at a temperature of 0 ° C to -45 ° C. As a result, the treated gas, which is mainly composed of methane and has a reduced H ₂ S concentration, is discharged from the head of the column 5 through the conduit 64, and H ₂ S and other absorption compounds are enriched from the bottom of the column. The liquid phase consisting of the solvent, which is contained in concentration, is discharged via the conduit 8.

The liquid phase exiting column 70 via conduit 71 is distilled in column 72 so that condensate exits the column via conduit 73 and the vapor phase exits column 72 via conduit 72. Is discharged. This vapor phase is then cooled in the cooling zone 75 and then merges with the high-concentration solvent flowing in the conduit 8 to form a liquid phase called rich solvent. This rich solvent flows in the conduit 9a. The temperature of the cooling process in the tower 70 is 0
The temperature is selected in the range of ℃ to -30 ℃, and the contact between the pretreatment gas mixture and the solvent in the column 5 is performed at a sufficiently low temperature in the range of 0 ℃ to -45 ℃. Further, the mass flow ratio of the processing gas mixture and the solvent is such that the processed gas collected at the head of the column 5 via the conduit 64 has a H ₂ S partial pressure lower than 65 Pa, and the processing gas mixture is _{In the} case of containing COS and / or mercaptan other than ₂ S, it has a total partial pressure of sulfur-containing compound of less than 260 Pa, and the rich solvent flowing in the conduit 9a has C ₃ or more existing in the processing gas mixture. It is selected to contain at least 80 mol% of hydrocarbons. The column 5 comprises two coolers 61a and 61b through which the fluid medium, ie the mixture of solvent and gas to be treated, passes, the medium indirectly exchanging heat with the cooling fluid via these coolers. Therefore, heating of the medium due to absorption is limited and the temperature profile in the column becomes uniform.

The rich solvent flowing through conduit 9a is introduced into the upper portion of expansion flask 29 where it expands to an intermediate pressure which releases much of the methane dissolved in the rich solvent, resulting in the first high methane concentration gas and methane pre-removal. A rich solvent is formed. The first enriched methane gas exits the top of flask 29 via conduit 34 and the methane pre-removal rich solvent exits the bottom of flask 29 via conduit 35. The methane pre-removal rich solvent is subjected to a second expansion treatment and further distilled in a distillation column 9 including a reboil system 30. As a result, a second high methane concentration gas discharged from the head of the column 9 via the conduit 32 and a methane-removed rich solvent with a reduced methane concentration discharged from the bottom of the column 9 via the conduit 11 are referred to. A liquid phase is formed. Said second methane-rich gas flowing in conduit 32 is sent to compressor 33 and is then discharged from said compressor via conduit 36 at about the same pressure as the first methane-rich gas flowing in conduit 34. These two methane-rich gases are mixed in conduit 10 and the vapor phase of this mixture is sent through compressor 23 to cooling zone 76 where it is at about the same temperature as the pretreated gas mixture flowing in conduit 3. To be cooled. The gas phase flowing out of the cooling zone 76 is partially liquefied. This partially liquefied phase is introduced into the separator 77, where it is separated into a liquid phase and a gas phase. The liquid phase exits the separator via conduit 79 and joins the enriched solvent flowing in conduit 8 and the gas phase is discharged from the separator 77 via conduit 78 and the pretreated gas mixture flowing in conduit 3. Join up with.

The methane removal rich solvent is sent to the cooling zone 12,
Then, for example, it is cooled to a temperature in the range of -25 ° C to -80 ° C and sufficiently lower than the temperature in the cleaning zone 5. As a result, demixion of the methane removal rich solvent is generated, so that the solvent is separated into the lower liquid fraction and the upper liquid fraction in the separator 12a. The lower liquid fraction is referred to as a purified solvent, and in some cases in addition to the acidic compound H ₂ S, CO ₂ , COS and mercaptan are also contained in a dissolved state, and further, a solution containing a very small amount of hydrocarbons,
It exits the separator via conduit 14. The upper liquid fraction is also referred to as the heavy first hydrocarbon fraction,
It is discharged from the separator 12a via 37.

The purified rich solvent flowing through conduit 14 is then subjected to the regeneration process described with reference to FIG. as a result,
A regenerated solvent and an acidic gas stream as obtained above by the process, i.e. an acidic gas stream having a hydrocarbon content expressed in methane equivalents of less than 5 mol% of the acidic compounds, is formed, said regenerated solvent in cooling zone 22. After being cooled to a temperature suitable for injecting into the column 5 therethrough, it is sent to the column 5 via the conduit 6.

In order to supplement the above description, four examples of the method of the present invention will be given below.

Example 1: A gas mixture having the following molar composition was treated using an apparatus similar to the one functioning as previously described briefly in FIG. 2: Methane: 69% Ethane: 3% Propane : 1% ・ Butane: 1% ・ Hexane: 1% ・ H ₂ S: 15% ・ CO ₂ : 10% Flow rate 20,000Kmoles / h, temperature 30 ℃ and pressure 5MPa 1
The gas mixture to be treated introduced via the is mixed with the high methane-concentrated gas phase formed as a result of the methane removal treatment of the rich solvent and delivered from the compressor 23, and the resulting gas mixture is cooled in the cooling zone 2. Cooled to 10 ° C. As a result of this cooling, 872 Kmoles / h of condensate is discharged from the separator 2a via line 4 and 21,039 Kmoles / h of pretreatment gas is drawn in line 3.
Flowed out of the separator 2a via. The molar composition of the gases was as follows: methane: 70.31% ethane: 3.20% propane: 0.85% - butane: 0.51% - _{hexane: 0.11% · H 2 S:} 13.89% · CO 2: 11.13 % The pretreatment gas mixture was contacted in the wash column 5 with a solvent of pure methanol at 14,000 Kmoles / h. The column 5 includes 28 theoretical plates for washing and is equipped with two coolers 61 on the side, one of which is arranged at the level of the first plate and the other is at the level of the 28th plate. And had outputs of 40 and 37.8 G Joules / h, respectively. These coolers serve to limit the temperature rise due to absorption and make the temperature profile in the column 5 uniform within an error of ± 5 ° C. The operating temperature of the column was −10 ° C.

As a result, a composition having the following mol% composition was discharged from the head of the column 5 at a pressure of 4959 KPa and a temperature of −10 ° C .: • Methane: 91.71 • Ethane: 2.99 • Propane: 0 • Butane: 0 • Hexane: 0 · H ₂ S: 10p.pm (volume) · CO _2: 5.06 · methanol: H ₂ S partial pressure of 0.09 the used gas mixture was equal to 50 Pa.

The treated gas mixture discharged from the column 5 via the conduit 64 is cooled to −45 ° C. in the cooling 55 zone, and 90% of the methanol flowing out of the washing column 5 together with the gas mixture is cooled.
% Or more was condensed in the separator 56. The liquid fraction produced by the condensation in the separator 56 and discharged from the separator via the conduit 57 at a flow rate of 15 Kmoles / h contained mainly methanol and CO ₂ .

The condensate discharged from the separator 2a via the conduit 4, the concentrated solvent of the acidic compound discharged from the column 5 via the conduit 8 and the liquid fraction discharged from the separator 56 via the conduit 57 are Combined with each other to make up the rich solvent to be subjected to methane removal treatment. The flow rate of this rich solvent is 21,270
Kmoles / h, the composition of which was mol% was as follows: ・ Methane: 5.96 ・ Ethane: 1.34 ・ Propane: 0.97 ・ Butane: 0.99 ・ Hexane: 0.95 ・ Methanol: 65.82 ・ H ₂ S: 15.91 ・CO ₂ : 8.05 The methane removal treatment of the rich solvent was started by first subjecting the solvent to the first expansion treatment in the flask 29 to expand it to a pressure of 2420 KPa to separate 61% of the dissolved methane. As a result, a gas containing 68 mol% of methane was generated in the flask 29.
From the head at 1149 Kmoles / h via conduit 34 and the methane pre-removed rich solvent was discharged from the flask via conduit 35. Next, the methane pre-removal rich solvent was subjected to a second expansion treatment to expand it to 1050 KPa, and then distilled in a column 9 containing 11 theoretical plates. As a result of reboiling with the gas mixture to be treated in the column, a second high methane concentration gas leaves at the head of column 9 via conduit 32 at 1148 Kmoles / h and a methane removal rich solvent It was obtained at a temperature of 13 ° C. and a pressure of 1070 KPa. The mol% composition of this solvent was as follows: ・ Methane: 0.02 ・ Ethane: 0.79 ・ Propane: 0.94 ・ Butane: 1.05 ・ Hexane: 1.05 ・ Methanol: 73.78 ・ H ₂ S: 15.81 ・ CO ₂ : 6.54 Said The second high methane concentration gas was compressed to 2420 KPa in the compressor 33 and then mixed with the first high methane concentration gas to form a gas phase with high methane concentration. This gas phase was sent through the compressor 23 toward the processing gas mixture for reuse.

The methane removal rich medium was cooled to −75 ° C. in the cooling zone 12 to cause mutual separation of constituent parts. as a result,
The solvent is separated into two fractions by a separator 12a,
The heavy first hydrocarbon fraction was discharged via conduit 37 and the pre-purified solvent was discharged via conduit 38.

The予精made solvent had mole% of the following composition: methane: 0.02 ethane 0.55 propane 0.58 - Butane 0.45 - hexane: 0.09 _{Methanol: 76.20 · H 2 S: 15.54} · CO 2: 6.58 The pre-purified solvent flowing through conduit 38 contains 5 theoretical plates −
In a liquid-liquid extractor 39 operating at 75 ° C., it was contacted with an extractant of 600 Kmoles / h mainly consisting of hexane. As a result of this contact, a liquid second hydrocarbon fraction is passed to the device 39 via conduit 62.
And purified solvent was extracted via conduit 14.

Said purifying solvent had mole% of the following composition: methane: 0.01 ethane 0.08 propane 0.04 - Butane 0.01 - hexane: 0.12 _{Methanol: 79.08 · H 2 S: 15.54} · CO 2: 6.40 The mixture formed by the combination of the second hydrocarbon fraction flowing in conduit 62 and the first hydrocarbon fraction flowing in conduit 37 is reheated in reheater 41 and then distilled in column 42 to remove heavy It was fractionated into a hydrocarbon fraction and a liquid fraction consisting of extractant. The heavy hydrocarbon fraction contains 96 mol% or more of C ₃ or more hydrocarbons contained in the processing gas mixture supplied via the conduit 1, and is discharged via the conduit 13 to obtain the liquid. The fraction was discharged via conduit 43. Most of the extractant was cooled to −75 ° C. in cooling zone 44 and then sent via conduit 40 to extractor 39.

The purified rich solvent flowing through conduit 14 was subjected to a regeneration process that included a partial regeneration step followed by a complete regeneration step. In order to carry out the partial regeneration operation, the purified rich solvent is first expanded to 230 KPa through the expansion valve 15 and then subjected to the first partial evaporation treatment by reheating in the reheater 46 to -25 ° C. It was As a result, the solvent is separated by the separator 46.
A first acid gas fraction of 1767 Kmoles / h, separated in a, was recovered via line 47 and the first liquid phase was discharged via line 50. The liquid phase was further subjected to a second partial evaporation treatment by heating it to 7 ° C. under a pressure of 190 KPa in a reheater 16, resulting in the liquid phase being separated in a separator 16a,
A second acid gas fraction of 133 Kmoles / h is discharged via conduit 17 and the semi-regenerated solvent at a temperature equal to 7 ° C. in conduit 18
Was discharged through.

To completely regenerate the semi-regenerated solvent, first remove the solvent at 450 KPa.
It was started by pumping up to and then splitting the solvent into two streams. One stream is introduced at a flow rate of 5000 Kmoles / h via conduit 51 into the head plate of a distillation column 20 operating at a pressure of 350 KPa, the other stream is a heat exchanger 52a from column 20 to conduit 21. It was reheated to 88 ° C. by indirect heat exchange with the regenerated solvent discharged via and then introduced into the seventh theoretical stage of column 20. As a result of distillation treatment of the semi-regenerated solvent in the column 20, an acid gas fraction of 799 Kmoles / h was recovered via the conduit 19 and the regenerated solvent was discharged via the conduit 21. The regeneration solvent is 30 ℃
Is discharged from the heat exchanger 52a at a temperature of
After being cooled to 0 ° C., it was sent to column 5 via conduit 6.

The first acid gas fraction flowing through conduit 47 is the reheater
After being heated to 7 ° C. at 49, it merges with the second acid gas fraction flowing through conduit 17 and the acid gas fraction discharged from column 20 via conduit 19, pressure 190 KPa, flow rate.
An acid gas stream of 3699 Kmoles / h was formed. The acid gas stream further contained 1.9 mol% hydrocarbons, expressed as methane equivalents, and 1.14 wt% methanol. The H ₂ S: CO ₂ molar ratio of the gas mixture to be treated was 1.5, whereas the ratio of the acid gas stream was equal to 2.22.

The acid gas stream flowing through conduit 24 was then subjected to a general wash treatment with water before being sent to the CLAUS sulfur unit.

Examples 2-4 A gas mixture of the same composition as the gas mixture treated in Example 1 was again used at the same flow rate, temperature and pressure using a device similar to the device functioning as previously described briefly in FIG. Processed.

The solvent used varied from example to example and consisted of pure propylene carbonate (Example 2), pure dimethylformamide (Example 3) and pure γ-butyrolactone (Example 4).

 The following operating methods were used in these three examples.

Cooling the gas mixture to be treated in column 70 to -24 ° C,
1226 Kmoles / h of condensate was recovered via conduit 71 and
774 Kmoles / h of pre-treated gas mixture via line 3 in tower 70
Discharged from.

The pretreatment gas had the following mol% composition in these three examples.

・ Methane: 72.35 ・ Ethane: 2.96 ・ Propane: 0.79 ・ Butane: 0.02 ・ Hexane: 0. ・ H ₂ S: 13.67 ・ CO ₂ : 10.21 The column 5 in which this pretreatment gas mixture is contacted with a solvent is a theoretical plate. 21 coolers 61 and two side coolers 61a and 6
Equipped with 1b. The coolers were placed on the 11th and 21st plates, respectively, and their outputs were chosen to limit the temperature rise due to absorption to keep the temperature profile in the column uniform within an error of ± 5 ° C.

From the head of the column 5 through conduit 64, treated gas having a H ₂ S content corresponding to equal H ₂ S partial pressure in the pressure and 5Pa of 4950KPa was recovered.

At the bottom of the column 5, a liquid phase consisting of a solvent containing H ₂ S and other absorbing compounds in high concentration flowed out via the conduit 8.

The condensate formed in column 70 was distilled in column 72, resulting in the formation of new condensate and gas. The condensate exited the column via conduit 73 and the gas was cooled to -25 ° C in cooling zone 75 and then mixed with the enriched solvent flowing in conduit 8 for methane removal treatment.

Methane removal treatment of rich pure solvent flowing in the conduit 9a is 2
Carried out in one step. First, in the expansion flask 29,
Expansion to a pressure of 2450 kPa, which causes about 80% of the methane dissolved in the solvent to separate, results in the first high methane concentration gas being discharged via conduit 34 and the methane pre-removed rich solvent being conduit 35. Was discharged through. Second of 1000kPa
As a result of the expansion treatment, and then the distillation treatment in the distillation column 9 equipped with 14 theoretical plates, the second high methane concentration gas is discharged via the conduit 32, and the methane removal rich solvent is at a temperature of 5 ° C. and 1000 kPa. Obtained in conduit 11 at a pressure of. The second high methane concentration gas was compressed in compressor 33 to 2400 kPa, then mixed with the first high methane concentration gas in conduit 10, and the resulting mixture was compressed in compressor 23 to 5500 KPa. The high-methane compressed gas discharged from the compressor 23 is passed through a cooling zone 76 where it is cooled to −25 ° C. and partially liquefied, and the partially liquefied fluid flowing out of the zone 76 is separated into a separator.
Introduced in 77. The gas fraction discharged from the separator via conduit 78 merges with the pretreatment gas mixture introduced into the washing column 5, and the liquid phase discharged from the separator via conduit 79 is passed through the conduit 8 to the column. Combined with the enriched solvent flowing out from No. 5.

The methane-depleted rich solvent flowing out via the conduit 11 is cooled in the cooling zone 12 to cause component mutual separation, and is separated into two fractions in the separator 12a, so that the liquid hydrocarbon fraction is separated via the conduit 37. Evacuated and purified solvent flowed out via conduit 14.

The purified solvent was further subjected to a regeneration process, as described in Example 1, which included a partial regeneration step followed by a complete regeneration step, resulting in a very low hydrocarbon content acid gas stream being discharged via conduit 24. And the regenerated solvent was recovered via conduit 21. This regenerated solvent is in the cooling zone
After cooling to −25 ° C. at 22, it was sent via conduit 6 towards wash column 5.

 The specific operating conditions and results for each example are shown in the table below.

Claims (17)

(57) [Claims] 1. A method for simultaneously performing selective desulfurization and gasoline removal treatment of a gas mixture which is mainly composed of methane and also contains hydrocarbons of H ₂ S and C ₂ or more and is under an absolute pressure of more than 0.5 MPa. Then, the gas mixture is preferentially dissolved in H ₂ S in the cleaning zone (5) and has a boiling point of 4 at atmospheric pressure.
The solvent (6) composed of a liquid having a viscosity higher than 0 ° C and a viscosity at -40 ° C of less than 0.1 Pa.s is brought into contact with the solvent, and the solvent absorbing H ₂ S is regenerated, and the regenerated solvent is recycled to the washing zone. It is a method of circulating, the contact operation of the gas mixture and the solvent at a temperature of 0 ℃ ~ -45 ℃, and the mass flow ratio of the gas mixture and the solvent to be treated and the theoretical plate number for cleaning is mainly composed of methane. and H ₂ S partial pressure 65Pa smaller treated gas (64), 80 mole% of C ₃ and higher hydrocarbons present the H ₂ S in the gas mixture to be a solvent as well as processing including a high concentration
A liquid phase (8) called a rich solvent composed of condensed hydrocarbon fractions corresponding to the above is selected to be formed, and the rich solvent is subjected to at least partial methane removal treatment (29, 9) to produce methane. A liquid phase called a methane removal rich solvent (11) having a reduced concentration and a gas phase (10) having a high methane concentration are formed, and the methane removal rich solvent is lower than the temperature in the washing zone at -25 to -80 ° C. (12) by cooling to a temperature of 10 ° C. to cause mutual separation of constituent parts of the methane removal-rich solvent, thereby containing an acidic compound H ₂ S and having a hydrocarbon content expressed as methane equivalent of 5 mol% of the acidic compound amount. The lower liquid fraction (38), referred to as the lower refined rich solvent, and the upper liquid fraction (the heavy hydrocarbons first fraction, consisting of the remainder of the hydrocarbons present in the methane removal rich solvent ( 37) and the heavy hydrocarbon first fraction is separated from the purified rich solvent, and the purified rich solvent is subjected to a regeneration treatment (46, 16, 20) to produce H ₂ S.
To form a regeneration solvent (21) and an acidic gas stream (24) containing almost all of the hydrocarbons and less than 5 mol% of hydrocarbons represented by methane equivalent, and the regeneration solvent is directed toward the washing zone (5). And recirculating (6). 2. Mainly consisting of methane, also containing H ₂ S and C ₂ or more hydrocarbons, and further containing one or more gaseous compounds of inert gas, H ₂ O, CO ₂ , COS and mercaptan,
A method for simultaneously performing selective desulfurization and gasoline removal treatment of a gas mixture under an absolute pressure of more than 0.5 MPa, wherein the gas mixture is treated with H ₂ S, C in a cleaning zone (5).
OS and mercaptan are preferentially dissolved, CO ₂ is partially dissolved, and the boiling point at atmospheric pressure is higher than 40 ° C, and the viscosity at -40 ° C is a solvent (6) consisting of a liquid smaller than 0.1 Pa.s. It is a method of contacting and regenerating the solvent that has absorbed H ₂ S and other compounds, and recycling the regenerated solvent to the washing zone. The contacting operation of the gas mixture and the solvent is from 0 ° C to -45 ° C. A treated gas (64) having a total partial pressure of a sulfur-containing compound mainly composed of methane at a temperature of ℃ and a mass flow ratio of a gas mixture and a solvent to be treated and a theoretical plate number for cleaning (64), and H ₂ S And a liquid phase called a rich solvent comprising a high concentration of other absorbing compounds and a condensed hydrocarbon fraction corresponding to 80 mol% or more of C ₃ or more hydrocarbons present in the gas mixture to be treated (8) And will be formed Performed selectively to the said rich solvent at least partial methane removal process (29,
9) Liquid phase called methane removal rich solvent (11) with reduced methane concentration and gas phase with high methane concentration (10)
And cooling the methane removal rich solvent to a temperature of -25 to -80 ° C below the temperature in the wash zone (12) to cause component separation of the methane removal rich solvent, In addition to the acidic compound H ₂ S, C dissolved in a solvent
A lower liquid fraction (38) referred to as a purified rich solvent containing O ₂ , COS and mercaptan and having a hydrocarbon content, expressed in methane equivalents, of less than 5 mol% of the amount of acidic compounds,
An upper liquid fraction (37) called a heavy hydrocarbon first fraction consisting of the remaining hydrocarbons present in the methane removal rich solvent is formed, and the heavy hydrocarbon first fraction is formed into the refined rich fraction. After separation from the solvent, the purified rich solvent is subjected to a regeneration treatment (46, 16, 20) to contain almost all of H ₂ S and other acidic compounds present in the purified rich solvent, and the acidic compound expressed as methane equivalent. Of an acidic gas stream (24) containing less than 5 mol% of hydrocarbons and a regenerating solvent (21) and recycling the regenerating solvent in the direction of the washing zone (5) (6). . 3. The solvent in contact with the gas mixture to be treated is 0.
A viscosity of less than 05 Pa.s.
Or the method described in 2. 4. The solvent which comes into contact with the gas mixture to be treated consists of one or more organic liquid absorbents used in anhydrous form or in the form of a mixture with water, these one or more absorbents being: formula An amide of the formula An aldehyde represented by the formula below Acetal represented by the formula below An ester represented by: C _{1 to} C ₄ alkanol, a diether of the formula CH ₃ OC ₂ H ₄ O _n CH _3, a diether alcohol of the formula R ₉ O—C ₂ H ₄ —O—C ₂ H ₄ —OH, formula Lactone and propylene carbonate [wherein R ₁ and R ₂ are the same or different from each other and represent a hydrogen atom or a C ₁ or C ₂ alkyl group, and R ₃ is C ₃ or
Alkyl of C _4, R ₄ and R ₅ are the same or different from each other, represent an alkyl group of C ₁ ~C _3, R ₆ is C ₂ -C ₄ alkyl group or a group C ₂ H ₄ O _n R ₈ [wherein R ₈ represents a C ₁ or C ₂ alkyl group, n is equal to 1 or 2], and R ₇ is
An alkyl group or a group of C ₁ or _{C 2 C 2 H 4 O n} R 8,
R ₉ is a C _{1 to} C ₄ alkyl group, and p is an integer of 2 to 4].
The method described in. 5. A wash zone for contacting a gas mixture to be treated with a solvent comprises one or more wash columns, each wash column comprising at least 10 theoretical stages for washing, preferably at least 20 theoretical stages. Method according to any of claims 1 to 4, characterized. 6. The temperature in each washing column is set to 1 for that column.
Due to the indirect heat exchange (61) between the fluid medium in the column and the cooling fluid occurring at one or more points, preferably ± 5
Method according to claim 5, characterized in that it is kept within an error of ° C. 7. A condensate containing predominantly C ₃ or higher hydrocarbons and H ₂ S, cooled (2) to a temperature of 0 ° C. to −30 ° C. before the gas mixture to be treated is contacted with a solvent. Liquid phase called (4)
And forming a gas phase (3) called a pretreatment gas mixture,
The pretreated gas mixture is then contacted with a solvent in the wash zone (5) and the solvent (8) exiting the wash zone is combined with the condensate (4) resulting from the cooling step in a rich solvent (9a). The method according to claim 1, wherein the rich solvent is subjected to a methane removal treatment. 8. The to be gaseous mixture treated was cooled (2) to a temperature of 0 ℃ ~-30 ℃ prior to contact with the solvent, and the condensate mainly containing C ₃ and higher hydrocarbons and H ₂ S Liquid phase called (4)
And forming a gas phase (3) called a pretreatment gas mixture,
The pre-treated gas mixture is then contacted with a solvent in the wash zone, the liquid phase consisting of the solvent (8) exiting the wash zone and the condensate (4) resulting from the cooling step (2).
And a liquid phase consisting of methane removal treatment, and the gas phases generated by these methane removal treatments are separately or mixed and optionally in the direction of the gas mixture (1) to be treated upstream of the cooling step (2). 7. Process according to any of claims 1 to 6, characterized in that the solvent and condensate after recycling to the separate methane removal treatment are combined to form a methane removal rich solvent (11). . 9. A methane removal treatment applied to a rich solvent and a condensate is performed in two steps, and in a first step, a fluid to be methane removal treated, that is, a rich solvent or a condensate is added to the fluid to be methane removed. A first expansion treatment (29) in which much of the dissolved methane is released to an intermediate pressure suitable for forming a first high methane concentration gas (34) and a methane pre-removal fluid (35), In the second step, the methane pre-removal fluid is subjected to a second expansion treatment and then a distillation treatment (9) to produce a second high methane concentration gas (32).
And a methane removal fluid (11) are formed, the second high methane concentration gas is compressed to the pressure of the first high methane concentration gas, and then mixed with the first high methane concentration gas to obtain a gas with high methane concentration. 9. The method according to any one of claims 1 to 8, characterized in that the phase (10) is formed. 10. At least a portion of a gas mixture taken from the gas mixture to be treated before contacting with a solvent or cooling before the distillation treatment (9) in the second step of the methane removal treatment, which follows the second expansion treatment, or 10. Process according to claim 9, characterized in that it is carried out by means of reboiling carried out in at least two reboiling zones (30a, 30b) arranged in series with a fluid (31) consisting of a part of the regenerating solvent. . 11. Regeneration treatment of the purified rich solvent is carried out by treating the purified rich solvent at a pressure higher than 100 KPa, preferably 150 KPa to 30.
Expansion to a pressure of 0 KPa (15) and then subjecting said expansion solvent to at least one partial evaporation treatment (46, 16),
At least one acidic gas fraction (47, 17) and a semi-regenerated solvent (1) whose temperature is at least 0 ° C. and whose pressure is less than the pressure of said expanding solvent and at least 100 KPa.
8) The semi-regenerated solvent is completely regenerated by a partial regeneration step to form and a distillation (20) mainly using reboil to produce an acidic gas fraction (19) and a regenerated solvent (2).
1) and a complete regeneration step to form a regenerated solvent, after which the regenerated solvent is appropriately cooled (22) and recirculated (6) in the direction of the washing zone (5) to produce various acidic gas fractions (47,
17. The method according to claim 1, wherein 17 and 19) combine with each other to form an acid gas stream (24) containing hydrocarbons in terms of methane equivalents in a concentration of less than 5 mol% of the acid compounds. The method described in. 12. The partial evaporation treatment of the expanded solvent in the partial regeneration step of the purified rich solvent is carried out by first subjecting the solvent to a first partial evaporation treatment (46) to obtain a first acidic gas fraction (47), Forming a first liquid phase (50) having a temperature below 0 ° C., and then subjecting said first liquid phase to a second partial evaporation treatment (16) to give a second acidic gas fraction (17), A temperature of 0 ° C. or higher and a pressure lower than the pressure of the expanding solvent to form a second liquid phase (18) equal to at least 100 KPa, and the second liquid phase is completely regenerated as a semi-regenerated solvent. Resulting in a complete regeneration treatment of the second acid gas fraction (17) and the semi-regenerated solvent after the first acid gas fraction (47) was reheated (49) to a temperature above 0 ° C. (49). Combined with the sour gas fraction (19), charcoal The method of claim 11, wherein the hydrogen content to form the acid gas stream (24) is less than 5 mol% of the acidic compound expressed in methane equivalent. 13. A complete regeneration treatment of a semi-regenerated solvent by distillation is carried out by using a column (20) including a plurality of theoretical stages and adapted to discharge (21) the regenerated solvent from the bottom. The regenerated solvent is separated into two streams and one stream (5
1) is sent to the head plate of the distillation column, and the other stream (52) is reheated countercurrently with the regenerated solvent discharged from the column (52a) before being introduced to the intermediate theoretical plate level of the column. 13. The method according to claim 11 or 12, characterized by: 14. A refined rich solvent (11) is subjected to a supplemental treatment for hydrocarbon removal prior to regeneration, which treatment preferably comprises a first liquid-liquid extraction zone (39) comprising four or more theoretical stages for extraction. ), Contacting the solvent with an extractant consisting mainly of a hydrocarbon having a molecular mass greater than n-pentane to separate a second hydrocarbon liquid fraction (62) from the refined rich solvent; The fraction (62) is combined with the first heavy hydrocarbon fraction (37) and the mixture thus formed is heated (41) and subjected to a distillation treatment (42) to give a gas mixture to be treated. Forming a heavy hydrocarbon fraction (13) containing 80 mol% or more of C ₃ or more hydrocarbons present in the extractant (4
3) is recovered and most of it is cooled (44) to a temperature almost the same as the temperature at which mutual separation of constituent components of the methane removal rich solvent occurs (44), and then re-cooled toward the first liquid-liquid extraction zone (39). A method comprising: circulating.
The method according to any one of 13 to 13. 15. The treated gas flowing out of the washing zone is cooled (55) by at least 15 ° C. to form a cooled treated gas (58) and a liquid fraction (57), the liquid fraction being a rich solvent. The method according to any one of claims 1 to 14, which is mixed with (9a) and subjected to a methane removal treatment. 16. The chilled gas is subjected to a complementary extraction process in a complementary extraction zone (60) with an extractant portion (45) not used in the first extraction zone (39) to obtain a higher purity. Treated gas (7) and liquid fraction (61)
16. Process according to claim 14 or 15, characterized in that the liquid fraction is formed and this liquid fraction is recycled for use in the distillation (41, 42) of the first and second hydrocarbon cut mixtures. 17. Prior to all treatments, the gas mixture to be treated is subjected to drying by distillation (15) and benzene removal operations and contact with anhydrous solvents, in particular the content of aromatic hydrocarbons, especially benzene, of 0.1. A liquid consisting of less than wt% dry gas inclusions (26), a hydrocarbon fraction (27) containing most of the aromatic hydrocarbons present in the gas mixture to be treated, and a solvent containing water ( 28) The method according to any one of claims 1 to 16, characterized in that